It has been shown that the male hormone androgen plays an important role in prostate cancer, benign prostatic hypertrophy, male pattern baldness, sexual precociousness, acnevulgaris, seborrhea and hypertrichosis. For example, it is known that persons who have been castrated and persons suffering from sexual gland failure almost never develop prostate cancer or benign prostatic hypertrophy.
For example, cyproterone acetate, chlormadinone acetate, flutamide, bicalutamide and the like are already used as anti-androgen agents, i.e., androgen receptor antagonists. These anti-androgen agents show an effect in many cases such as drug therapy in prostate cancer, and are important treatment agents in this area. In addition, it is known that cyproterone acetate suppresses the progression of acne in teenagers and the occurrence of baldness. Furthermore, in females, cyproterone acetate is used in the treatment of androgenization and hair loss. Flutamide and bicalutamide are used as drugs for prostate cancer treatment.
However, as problems encountered in these anti-androgen agents, it is known that even if the anti-androgen agents are effective, the disease recurs in almost all cases in two to five years, and in such cases, androgen resistance appears.
Furthermore, it has been reported that hydroxyflutamide, which is the active form of flutamide, causes an increase in androgen receptor transcription activity at a concentration of 10 μmol/L. Moreover, the hydroxyflutamide concentration in the blood in prostate cancer patients treated with flutamide is several μmol/L. However, it has been reported that this concentration reaches a concentration at which hydroxyflutamide shows an agonist effect (see Non-patent Document 1).
Furthermore, it has been reported that there is an increase in the weight of the prostate gland when cyproterone acetate and chlormadinone acetate are continuously administered to castrated rats for two weeks (see Non-patent Document 2). Moreover, in regard to flutamide and bicalutamide, there are also reports of side effects such as liver toxicity and the like. Accordingly, there is a demand for an anti-androgen agent which has a sufficient antagonistic effect, and in which these problems have been solved.
Meanwhile, the compounds represented by the following formula described in JP 04-308579 A (Patent Document 1) and the corresponding European Patent Application No. 494819 A (Patent Document 2) are known as phenylimidazolidines that show anti-androgen activity.

Furthermore, the compounds represented by the following formula described in JP 10-510845 A (Patent Document 3) and the corresponding WO 97/00071 A1 (Patent Document 4) are known as substituted phenylimidazolidines that show an anti-androgen activity.

However, the compounds neither constitute means for solving the problems of existing anti-androgen agents.
In the meantime, the compounds described in WO2004/031160 A1 (Patent Document 5) and WO2004/070050 A1 (Patent Document 6) are known as well-known imidazolidine derivatives having a substituent containing a cyclic group in 3-position, but these documents do not mention about an anti-androgen effect.    Patent Document 1: JP 04-308579 A    Patent Document 2: EP 494819 A1    Patent Document 3: JP 10-510845 A    Patent Document 4: WO 97/00071 A1    Patent Document 5: WO2004/031160 A1    Patent Document 6: WO2004/070050 A1    Non-Patent Document 1: J. Biol. Chem., Vol. 270, page 19998-20003, 1995    Non-Patent Document 2: Japanese journal of endocrinology, Vol. 66, page 597-606, 1990